Optically refractive materials diffusely refract light by scattering or bending light waves incident thereon. The eyes of an observer perceive brightness associated with the amount of light scattered from the surface. Various devices or structures, such as portable electronic devices, may be coated with optically refractive materials for functional and/or aesthetic purposes. For example, white surfaces are often used to impart a clean look and feel to a device. The greater the amount of light scattered by the white surface, the brighter and whiter the white surface appears to the eyes of an observer.
A portion of light incident to an optically refractive material may be reflected by the material and a portion may penetrate the material. When light that penetrates encounters an interface between different materials (such as between a carrier medium of the material and tinting pigments or other particles suspended in the medium), the direction of the light changes. This scattering event refracts the light. The greater the difference or mismatch in the indexes of refraction of the different materials, the larger the angle of the light's changed direction. Larger angles as compared to smaller ones result in the light encountering fewer interfaces (e.g., less scattering events) and penetrating less deeply into the optically refractive material before being refracted back out. As a result, the optically refractive material absorbs less and scatters more light.